Introduction

Artemisia selengensis Turcz. is a perennial herb belonging to the Compositae that grows mainly in wetlands, and waterside in Korea (Lee 1993). The aerial parts of this plant have been used traditionally as an anti-inflammation, hemostasis, invigorating the blood circulation, and relieving dysmenorrhea (Ahn 1998; Hu and Feng 1999). Only a few phytochemical investigation on this plant resulted in the isolation of a sesquiterpene endoperoxide, and sesquiterpene (Hu and Feng 1999; Jang and Lee 1993). Concerning the biological studies of A. selengensis, anti-tumor, antioxidant and immune-modulating activities of its various extracts has been reported so far (Koo et al. 1994; Shi et al. 2010).

In an ongoing investigation into anti-inflammatory compounds from natural products, the methanol extract of A. selengensis was found to inhibit IL-6 production in TNF-α stimulated MG-63 cells. By means of repeated column chromatography using silica gel, Sephadex LH-20, and LiChroprep RP-18, ten compounds were isolated from the aerial parts of A. selengensis. The structures of these compounds were identified as 1′,3′-propanediol,2′-amino-1′-(1,3-benzodioxol-5-yl) (1), artanomaloide (2), canin (3), eupatilin (4), quercetin-3-O-β-d-glucoside-7-O-α-l-rhamnoside (5), 1,3-di-O-caffeoylquinic acid (6), isoquercitrin (7), pinoresinol-4-O-β-d-glucoside (8), scopolin (9), and isofraxidin-7-O-β-d-glucopyranoside (10), by comparing their spectroscopic data with those reported in the literature. These compounds were isolated from this plant for the first time. Furthermore, compound 1 was isolated for the first time as a new natural product even though it was synthesized previously. For theses isolated compounds, the inhibitory activity of IL-6 production in TNF-α stimulated MG-63 cells was examined. Among these compounds, artanomaloide (2), and canin (3) showed potent inhibitory activity against IL-6 production in TNF-α stimulated MG-63 cells.

This paper reports the isolation, structure elucidation, and the inhibitory activity of IL-6 production of isolated compounds from the aerial parts of A. selengensis. In addition, the complete NMR assignments of compound 1 are presented here for the first time.

Materials and methods

General procedure

Optical rotations were measured using an Autopol-IV polarimeter (Rudolph Research Flangers). The UV spectra were obtained on a Shimadzu UV/Visible Spectrophotometer. The IR spectra were recorded on an IMS 85 (Bruker). The HR-TOF -MS spectra were recorded on a Q-TOF (Synapt HDMS system, Waters, USA) mass spectrometer. The NMR spectra were recorded on a Varian Unity Inova 500 and Unity Inova 600 spectrometer (KBSI-Gwangju center). Semi-preparative HPLC was performed using a Waters HPLC system equipped with Waters 600 Q-pumps, a 996 photodiode array detector, and a YMC-Pack ODS-A column (250 × 10 mm i.d., 5 μm), flow rate 4.0 mL/min. TLC and column chromatography were performed on precoated Si Gel F254 plates (Merck, art. 5715), RP-18 F254 plates (Merck, art. 15389) and silica gel 60 (40–63 and 63–200 μm, Merck), MCI gel CHP20P (75–150 μ, Mitsubishi Chemical Co.), Sephadex LH-20 (25–100 μm, Sigma), as well as LiChroprep RP-18 (40–63 μm, Merck).

Plant material

The aerial parts of A. selengensis Turcz. (Compositae) were collected from the Herbarium of College of Pharmacy, Chosun University, Korea, in Aug 2007. A voucher specimen was deposited in the Herbarium of College of Pharmacy, Chosun University (CSU-1041-17).

Extraction and isolation

The air-dried aerial parts of A. selengensis (3.5 kg) were extracted three times with MeOH under reflux and 218.9 g of residues were produced. The MeOH extract was suspended in water, which was then partitioned sequentially with equal volumes of dichloromethane (CH2Cl2), ethyl acetate (EtOAc) and n-butanol (BuOH). Each fraction was evaporated in vaccuo to yield residues of CH2Cl2 (61.8 g), EtOAc (12.1 g), n-BuOH (27.6 g), and water extract (117.4 g). The CH2Cl2 fraction (26.0 g) was chromatographed over a silica gel column chromatography (CC), using a gradient solvent system of Hexane:EtOAc (10:1 → 1:5), to give six subfractions (D1–D6). Subfraction D5 (1.70 g) was subjected to a silica gel CC eluting with a gradient solvent system of Hexane:EtOAc (3:1 → 1:2) to yield nine subfractions (D5-1–D5-9). Subfraction D5-5 (210.81 mg) was eluted with Hexane:Acetone (4:1) to yield thirteen subfractions (D5-5-1–D5-5-13). Subfraction D5-5-9 (41.84 mg) was subjected to RP-18 CC eluting with a gradient solvent system of MeOH: H2O (1:1.5 → 2:1) to give 2 (8.56 mg), 3 (9.12 mg), and 4 (3.53 mg), respectively. Subfraction D3 (3.1 g) was purified by repeated silica gel CC (Hexane:EtOAc, 10:1 → 2:1), followed by MCI gel CC (MeOH:H2O, 50:1), to give 1 (12.37 mg). The n-BuOH fraction (2.5 g) was chromatographed over a HP-20 CC, using a gradient solvent system of MeOH:H2O (0:100 → 100:0) to give six subfractions (B1–B6). Subfraction B4 (0.55 g) was subjected to a silica gel CC eluting with a gradient solvent system of CHCl3:MeOH:H2O (7.5:1:0.1 → 1:1:0.1) to yield twenty-four subfractions (B4-1–B4-24). Subfraction B4-18, -19, and -20 (61.09 mg) was eluted with CHCl3:MeOH:H2O (3:1:0.1) to yield 5 (4.18 mg), and 6 (3.77 mg). Subfraction B4-9-21, and -22 (39.24 mg) was purified by silica gel CC eluting with a gradient solvent system of CHCl3:MeOH:H2O (4:1:0.1 → 2:1:0.1), followed by Lichroprep RP-18 CC (MeOH:H2O, 1:3 → 1:2.5) to give 7 (3.07 mg), and 8 (3.10 mg). Subfraction B3 (2.54 g) was purified by MCI gel CC eluting with a gradient solvent system of MeOH:H2O (1:4 → 1:1), followed by silica gel CC (CHCl3:MeOH:H2O,10:1:0.1 → 1:1:0.1) to give 9 (6.78 mg), and 10 (1.49 mg).

1′,3′-Propanediol,2′-amino-1′-(1,3-benzodioxol-5-yl) (1)—White amorphous powder; \([\alpha ]_{\text{D}}^{25}\) 12.7° (CHCl3; c 0.1); HR-ESI-MS (positive mode) m/z: 212.0962 [M + H]+ (calcd for C10H14NO4, 212.0923); 1H NMR (500 MHz, CDCl3) δ: 3.05 (1H, dd, J = 4.5, 6.5 Hz, H-2′), 3.87(1H, dd, J = 3.5, 9.5 Hz, H-3′a), 4.23 (1H, dd, J = 6.5, 9.5 Hz, H-3′b), 4.71 (1H, d, J = 4.5 Hz, H-1′), 5.95 (2H, s, O-CH2-O), 6.78 (1H, d, J = 8.0 Hz, H-7), 6.80 (1H, dd, J = 1.5, 8.0 Hz, H-6), 6.85 (1H, br s, H-4); 13C NMR (125 MHz, CDCl3) δ: 101.0 (O-CH2-O), 106.5 (C-4), 134.9 (C-5), 119.3 (C-6), 108.1 (C-7), 147.9 (C-8), 147.0 (C-9), 85.7 (C-1′), 54.3 (C-2′), 71.7 (C-3′).

Artanomaloide (2)—Colorless gum; \([\alpha ]_{\text{D}}^{25}\) −17° (CHCl3; c 0.2); HR-EI-MS m/z: 548.2440 [M]+ (calcd for C32H36O8 548.2447); 1H NMR (500 MHz, CDCl3) δ: 1.23 (3H, s, H-14′), 1.51 (1H, d, J = 12.0 Hz, H-13a), 1.54 (3H, s, H-15′), 1.83 (2H, m, H-9′), 1.84 (1H, m, H-8′a), 1.98 (1H, d, J = 9.8 Hz, H-5′), 2.04 (3H, s, -OAc), 2.10 (1H, m, H-8′b), 2.31 (3H, br s, H-14), 2.36 (1H, d, J = 2.5 Hz, H-9a), 2.37 (3H, s, H-15), 2.43 (1H, d, J = 12.0 Hz, H-13b), 2.90 (1H, dd, J = 10.5, 13.0 Hz, H-9b), 3.06 (1H, m, H-7), 3.15 (1H, m, H-7′), 3.78 (1H,br d, H-6), 3.79 (1H, br d, H-5), 4.22 (1H, t, J = 9.5 Hz, H-6′), 5.15 (1H, dd. J = 2.5, 10.5 Hz, H-8), 5.47 (1H, d, J = 3.0 Hz, H-13′a), 5.88 (1H, d, J = 5.5 Hz, H-3′), 6.04 (1H, d, J = 3.0 Hz, H-13′b), 6.17 (1H, s, H-3), 6.28 (1H, d, J = 5.5 Hz, H-2′); 13C NMR (125 MHz, CDCl3) δ: 136.0 (C-1), 197.3 (C-2), 136.6 (C-3), 174.6 (C-4), 51.2 (C-5), 81.0 (C-6), 57.6 (C-7), 68.1 (C-8), 44.1 (C-9), 145.9 (C-10), 61.5 (C-11), 178.5 (C-12), 38.0 (C-13), 20.5 (C-14), 20.2 (C-15), 65.1 (C-1′), 143.3 (C-2′), 134.2 (C-3′), 58.2 (C-4′), 67.9 (C-5′), 81.9 (C-6′), 44.9 (C-7′), 22.1 (C-8′), 35.7 (C-9′), 73.1 (C-10′), 142.8 (C-11′), 172.7 (C-12′), 119.9 (C-13′), 29.6 (C-14′), 15.2 (C-15′), 25.0, 172.7 (OAc).

Canin (3)—Colorless powder; \([\alpha ]_{\text{D}}^{25}\) −14.7° (CHCl3; c 0.4); HR-ESI-MS (positive mode) m/z: 279.1236 [M + H]+ (calcd for C15H19O5 279.1230); 1H NMR (500 MHz, CDCl3) δ: 1.27 (3H, s, H-14), 1.57 (3H, s, H-15), 1.84 (1H, m, H-9a), 2.05 (1H, m, H-9b), 2.10 (1H, m, H-8a), 2.33 (1H, m, H-8b), 2.63 (1H, d, J = 11.5 Hz, H-5), 3.45 (1H, m, H-7), 3.70 (1H, br s, H-2), 4.07 (1H, br s, H-3), 4.34 (1H, dd, J = 9.5, 11.5 Hz, H-6), 5.49 (1H, d, J = 3.0 Hz, H-13a), 6.21 (1H, d, J = 3.0 Hz, H-13b); 13C NMR (125 MHz, CDCl3) δ: 73.3 (C-1), 64.6 (C-2), 64.3 (C-3), 83.3 (C-4), 57.8 (C-5), 79.8 (C-6), 45.0 (C-7), 23.5 (C-8), 35.0 (C-9), 72.2 (C-10), 139.3 (C-11), 169.4 (C-12), 120.0 (C-13), 26.5 (C-14), 22.1 (C-15).

Eupatilin (4)—Yellow amorphous powder; EI-MS m/z: 344 [M]+; 1H NMR (500 MHz, CDCl3) δ: 3.94 (3H, s, OCH3), 3.98 (3H, s, OCH3), 3.99 (3H, s, OCH3), 6.61 (1H, s, H-3), 6.56 (1H, s, H-8), 6.98 (1H, d, J = 9.0 Hz, H-5′), 7.34 (1H, d, J = 2.0 Hz, H-2′), 7.53 (1H, dd, J = 2.0, 8.5 Hz, H-6′); 13C NMR (125 MHz, CDCl3) δ: 163.9 (C-2), 104.5 (C-3), 182.6 (C-4), 153.2 (C-5), 132.6 (C-6), 158.7 (C-7), 90.6 (C-8), 153.1 (C-9), 106.1 (C-10), 123.8 (C-1′), 108.7 (C-2′), 149.3 (C-3′), 152.2 (C-4′), 111.1 (C-5′), 120.1 (C-6′), 60.86 (OCH3), 56.33 (OCH3), 56.11 (OCH3).

Quercetin-3-O-β-d-glucoside-7-O-α-l-rhamnoside (5)—Yellow amorphous powder; 1H NMR (500 MHz, CD3OD) δ: 1.12 (3H, d, J = 6.0 Hz, H-6′″), 3.08 (1H, m, H-4″), 3.24 (1H, d, J = 7.5 Hz, H-3″), 3.24 (1H, d, J = 7.5 Hz, H-2″), 3.29 (1H, d, J = 9.0 Hz, H-4″′), 3.31 (2H, m, H-6″), 3.40 (1H, m, H-5″′), 3.60 (1H, m, H-5″), 3.63 (1H, dd, J = 2.9, 9.5 Hz, H-3″″), 3.83 (1H, dd, J = 2.0, 2.9 Hz, H-2″′), 4.52 (d, J = 1.2 Hz, H-1″′), 5.11 (1H, d, J = 7.5 Hz, H-1″), 6.21 (1H, d, J = 2.0 Hz, H-6), 6.40 (1H, d, J = 2.0 Hz, H-8), 6.87 (1H, d, J = 8.5 Hz, H-5′), 7.63 (1H, dd, J = 2.0, 8.5 Hz, H-6′), 7.67 (1H, d, J = 2.0 Hz, H-2′); 13C NMR (125 MHz, CD3OD) δ: 159.4 (C-2), 135.7 (C-3), 179.6 (C-4), 163.1 (C-5), 100.2 (C-6), 166.5 (C-7), 95.1 (C-8), 158.7 (C-9), 104.9 (C-10), 123.7 (C-1′), 117.8 (C-2′), 146.0 (C-3′), 150.0 (C-4′), 116.2 (C-5′), 123.2 (C-6′), 105.7 (C-1″), 75.9 (C-2″), 76.4 (C-3″), 71.5 (C-4″), 78.3 (C-5″), 68.7 (C-6″), 102.6 (C-1″′), 74.1 (C-4″′), 71.4 (C-5″′), 72.3 (C-3″′), 69.9 (C-2″′), 18.0 (C-6″′).

Isoquercitrin (6)—Yellow amorphous powder; \([\alpha ]_{\text{D}}^{25}\) −85° (MeOH; c 0.06); EI-MS m/z: 464 [M]+; 1H NMR (500 MHz, CD3OD) δ: 3.71–3.35 (6H, m, H-2″-6″), 5.25 (1H, d, J = 8.0 Hz, H-1″), 6.20 (1H, d, J = 2.0 Hz, H-6), 6.39 (1H, d, J = 2.0 Hz, H-8), 6.87 (1H, d, J = 8.5 Hz, H-5′), 7.59 (1H, dd, J = 2.0, 8.5 Hz, H-6′), 7.78 (1H, d, J = 2.0 Hz, H-2′); 13C NMR (125 MHz, CD3OD) δ: 159.1 (C-2), 135.7 (C-3), 179.6 (C-4), 163.2 (C-5), 100.1 (C-6), 166.5 (C-7), 94.9 (C-8), 158.6 (C-9), 104.4 (C-10), 123.2 (C-1′), 117.7 (C-2′), 146.1 (C-3′), 150.0 (C-4′), 116.1 (C-5′), 123.3 (C-6′), 105.7 (C-1″), 75.9 (C-2″), 78.5 (C-3″), 71.3 (C-4″), 78.3 (C-5″), 62.7 (C-6″).

1,3-Di-O-caffeoylquinic acid (7) - Yellowish gum; \([\alpha ]_{\text{D}}^{25}\) −24.7° (MeOH; c 0.21); 1H NMR (500 MHz, CD3OD) δ: 1.98 (1H, m, H-6a), 2.25 (1H, dd, J = 3.5, 13.0 Hz, H-2b), 2.69 (2H, m, H-2a,-6b), 3.72 (1H, dd, J = 3.5, 9.5 Hz, H-4), 4.22 (1H, dd, J = 3.5, 6.5 Hz, H-5), 5.45 (1H, m, H-3) (quinic acid moiety); 6.32 (2H, d, J = 16.0 Hz, H-2), 6.77 (2H, dd, J = 2.5, 8.0 Hz, H-8), 6.94 (2H, dd, J = 2.0, 8.5 Hz, H-9), 7.05 (2H, t, J = 2.0 Hz, H-5), 7.57 (2H, dd, J = 4.5, 16.0 Hz, H-3) (caffeoyl groups); 13C NMR (125 MHz, CD3OD) δ: 82.7 (C-1), 35.5 (C-2), 70.5 (C-3), 73.2 (C-4), 69.6 (C-5), 37.1 (C-6), 176.8 (C-7) (quinic acid moiety); 167.8, 166.9 (C-1), 115.5, 114.2 (C-2), 145.5, 145.4 (C-3), 126.8, 126.5 (C-4), 113.7, 113.6 (C-5), 145.3, 144.8 (C-6), 148.2, 147.8 (C-7), 115.1, 115.0 (C-8), 121.6, 121.4 (C-9) (caffeoyl groups).

Pinoresinol-4-O-β-d-glucoside (8)—Yellow amorphous powder; \([\alpha ]_{\text{D}}^{25}\) −84.0° (MeOH; c 0.16); 1H NMR (500 MHz, CD3OD) δ: 3.13 (2H, m, H-8, 8′), 3.39–3.86 (sugar H), 3.84 (3H, s, OCH3), 3.85 (3H, s, OCH3), 3.86 (2H, m, H-9a, 9a′),4.24 (2H, m, H-9b, 9b′), 4.71 (1H, d, J = 4.0 Hz, H-7′), 4.76 (1H, d, J = 4.5 Hz, H-7), 4.87 (1H, H-1″), 6.77 (1H, d, J = 8.5 Hz, H-5′), 6.81 (1H, dd, J = 1.5, 8.5 Hz, H-6′), 6.92 (1H, dd, J = 1.5, 8.5 Hz, H-6), 6.94 (1H, d, J = 1.5 Hz, H-2′), 7.03 (1H, d, J = 2.0 Hz, H-2), 7.15 (1H, d, J = 8.0 Hz, H-5); 13C NMR (125 MHz, CD3OD) δ: 137.6 (C-1), 133.9 (C-1′), 111.7 (C-2), 111.1 (C-2′), 147.6 (C-3), 147.4 (C-3′), 151.1 (C-4), 149.3 (C-4′), 118.1 (C-5), 116.2 (C-5′), 119.9 (C-6), 120.2 (C-6′), 87.2 (C-7), 87.6 (C-7′), 55.5 (C-8), 55.7 (C-8′), 72.8 (C-9), 72.8 (C-9′), 56.9 (C-OCH3), 56.5 (C-OCH3), 102.9 (C-1″), 75.0 (C-2″), 78.0 (C-3″), 71.5 (C-4″), 78.3 (C-5″), 62.6 (C-6″).

Scopolin (9)—White powder; 1H NMR (500 MHz, DMSO-d 6): δ 3.15 (1H, m), 3.28 (2H, m), 3.45 (2H, m), 3.69 (1H, m), 3.82 (3H, s, 6-OCH3), 5.08 (1H, d, J = 7.5 Hz, H-1′), 6.33 (1H, d, J = 9.0 Hz, H-3), 7.15 (1H, s, H-8), 7.30 (1H, s, H-5), 7.96 (1H, d, J = 9.5 Hz, H-4); 13C NMR (125 MHz, DMSO-d 6) δ: 160.5 (C-2), 113.3 (C-3), 144.2 (C-4), 109.6 (C-5), 146.0 (C-6), 149.9 (C-7), 103.0 (C-8), 148.9 (C-9), 112.2 (C-10), 56.0 (6-OCH3), 99.6 (C-1′), 73.0 (C-2′), 76.7 (C-3′), 69.6 (C-4′), 77.1 (C-5′), 60.6 (C-6′).

Isofraxidin-7-O-β-d-glucopyranoside (10)—Colorless amorphous powder; \([\alpha ]_{\text{D}}^{25}\) +44.1° (MeOH; c 0.25); 1H NMR (500 MHz, DMSO-d 6) δ: 3.09 (2H, m), 3.24 (2H, m), 3.38 (1H, m), 3.59 (1H, m), 3.82 (3H, s, 6-OCH3), 3.91 (3H, s, 8-OCH3), 5.15 (1H, d, J = 5.0 Hz, H-1′), 6.40 (1H, d, J = 9.5 Hz, H-3), 7.13 (1H, s, H-5), 7.96 (1H, d, J = 9.5 Hz, H-4); 13C NMR (125 MHz, DMSO-d 6) δ: 159.8 (C-2), 114.7 (C-3), 144.4 (C-4), 105.4 (C-5), 149.4 (C-6), 141.6 (C-7), 140.2 (C-8), 142.4 (C-9), 114.5 (C-10), 56.5 (6-OCH3), 61.3 (8-OCH3), 102.2 (C-1′), 74.1 (C-2′), 77.5 (C-3′), 70.0 (C-4′), 76.5 (C-5′), 60.7 (C-6′).

Bioassay of IL-6

IL-6 bioassay was carried out using a slight modification of an established method (Kim et al. 2003; Liu et al. 2006). Briefly, 500 μL of the MG-63 cells (3 × 104 cells/mL) in DMEM containing 10 % FBS were dispensed into a 24-well plate; the culture was incubated for 24 h at 37 °C. Then, 5 μL of TNF-α (10 ng/mL), 5 μL of BAY 11-7085 (10 ng/mL), and 5 μL of the DMSO with or without the compounds (100 μg/mL) were added. After incubation at 37 °C with 5 % CO2 for 24 h, the medium was stored at −20 °C until measurement. The IL-6 content of the medium was measured in an ELISA procedure. 96-well plates were coated with 100 μL of purified rat anti-human IL-6 monoclonal antibody in 0.1 M NaHCO3 (pH 9.6) by overnight incubation at 4 °C. The wells were blocked with 200 μL of 3 % BSA in PBS for 2 h at room temperature (RT) and then incubated with 100 μL of specific antibody for 2 h at RT. 100 μL of HRP conjugated rabbit anti-goat IgG (1:1,000 dilution) was added to each well and incubated for 2 h at RT. 100 μL of TMB (3,3′,5,5′-tetramethylbenzidine) substrate solution was added and incubated for 10 min at RT. The color reaction was stopped with 50 μL of 0.4 N HCl and the optical density was read at 450 nm using a Microplate Reader (Molecular Devices Co., Ltd., U.S.A.).

Results and discussion

The MeOH extract of the aerial parts of A. selengensis was partitioned into CH2Cl2, EtOAc, n-BuOH-soluble fractions. Separation of the CH2Cl2 and n-BuOH soluble fraction with silica gel, MCI gel filtration, and repeated RP-18 CC led to the isolations of compounds 1–10 (Fig. 1).

Fig. 1
figure 1

Structures of compounds 1–10

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Compound 1 was obtained as white amorphous powder, \([\alpha ]_{\text{D}}^{25}\) 12.7° (MeOH). Its molecular formula was determined to be C10H14NO4 by HR-ESI-MS data at m/z 212.0962 [M+ H]+ (calcd for C10H14NO4 212.0923). In the IR spectrum, absorption bands for hydroxyl (3,400 cm−1) and aromatic ring (1600, 1518 cm−1) groups were observed. The 1H NMR spectrum of 1 showed ABX-trisubstituted aromatic protons at δH 6.78 (1H, d, J = 8.0 Hz, H-7), 6.80 (1H, dd, J = 1.0, 8.0 Hz, H-6), 6.85 (1H, br s, H-4), one hydroxyl propyl proton at δH 3.87(1H, dd, J = 3.5, 9.5 Hz, H-3′a), 4.23 (1H, dd, J = 6.5, 9.5 Hz, H-3′b), one oxymethine proton at δH 4.71 (1H, d, J = 4.5 Hz, H-1′), one aminomethine proton at δH 3.05 (1H, dd, J = 4.5, 6.5 Hz, H-2′) and one methylene dioxy proton at δH 5.95 (2H, s, H-2). In the 13C NMR spectrum, 10 carbon signals appeared, which included two oxygenated quaternary carbons at δC 147.9 (C-8), and 147.0 (C-9), three aromatic carbons at δC 106.5 (C-4), 119.3 (C-6), and 108.1 (C-7), one quaternary carbon at δC 134.9 (C-5), one oxygenated carbon at δC 85.7 (C-1′), one aminomethine carbon at δC 54.3 (C-2′), one methylene dioxycarbon at δC 101.0 (C-2) and one hydroxyl propyl carbon δC at 71.7 (C-3′). From these results, compound 1 was indicated to be a phenylpropanoid derivative with one amino and two hydroxyl groups. In the HMBC spectrum, correlations between H-2 and C-9/C-8, H-1′ and C-5/C-3′ were observed. Furthermore, in the 1H-1H COSY spectrum, the hydroxyl proton at δH 3.87 (H-3′a) and 4.23 (H-3′b) showed couplings with H-2′, and H-1′ (Fig. 2). Accordingly, compound 1 was determined as 1′,3′-propanediol,2′-amino-1′-(1,3-benzodioxol-5-yl), as shown in Fig. 1. Compound 1 was isolated for the first time as a new natural product even though it was synthesized previously (Cellitti et al. 2008). Furthermore, its spectral data are presented here for the first time.

Fig. 2
figure 2

Selected 1H-1H COSY (–), HMBC (H → C) correlations of compound 1

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Artanomaloide (2) was obtained as colorless gum, \([\alpha ]_{\text{D}}^{25}\) −17°. The 1H, 13C NMR, and HSQC spectroscopic data of 2 showed the presence of 32 carbons, which were assignable to four tertiary methyl groups [δH 1.23 (3H, s, H-14′), 1.54 (3H, s, H-15′), 2.31 (3H, br s, H-14), 2.37 (3H, s, H-15); δC 29.6 (C-14′), 15.2 (C-15′), 20.5 (C-14), 20.2 (C-15), respectively], three carbonyl groups [δC 197.3 (C-2), 178.5 (C-12), 172.7 (C-12′)], three acetal methine groups [δH 3.78 (1H, br s, H-6); δC 81.0 (C-6), δH 4.22 (1H, t, J = 9.5 Hz, H-6′); δC 81.9 (C-6′), δH 5.15 (1H, dd, J = 2.5, 10.5 Hz, H-8); δC 68.1 (C-8)], an exo methylene group [δH 5.47 (1H, d, J = 3.0 Hz, H-13′a) and δH 6.04 (1H, d, J = 3.0 Hz, H-13′b); δC 119.9 (C-13′)], one oxygenated quaternary carbon δC 73.1(C-10′), one acetyl group [δH 2.04 (3H, s); δC 172.7], two olefinic groups [δH 6.17 (1H, s, H-3); δC 136.6 (C-3), δH 5.88 (1H, d, J = 5.5 Hz, H-3′); δC 134.2 (C-3′), δH 6.28 (1H, d, J = 5.5 Hz, H-2′); δC 143.3 (C-2′), respectively], four methylene groups δC 44.1(C-9), 38.0 (C-13), 35.7 (C-9′), and 22.1 (C-8′), four methine groups [δH 1.98 (d, J = 9.8 Hz, H-5′); δC 67.9 (C-5′), δH 3.06 (1H, m, H-7); δC 57.6 (C-7), δH 3.15 (1H, m, H-7′); δC 44.9 (C-7′), δH 3.79 (1H, br s, H-5); δC 51.2 (C-5), respectively], and two quaternary carbons δC 65.1(C-1′) and 61.5 (C-11). From these results, compound 2 was indicated to be a dimeric sesquiterpene lactone (Jakupovic et al. 1987). Furthermore, in the HMBC spectrum, long range correlations between H-3/H-6 and C-1, H-7 and C-11, H-3 and C-2 were observed. In addition, correlations between H-5′ and C-11, H-7′ and C-12′, H-6′ and C-11′ were supported the proposed structure of 2. Accordingly, compound 2 was determined as artanomaloide on the basis of the above evidences, together with a comparison with the literature (Jakupovic et al. 1987).

Compound 3 was obtained colorless powder, \([\alpha ]_{\text{D}}^{25}\) −14.7°. The 1H-, 13C NMR, and HSQC spectroscopic data of 3 showed the presence of 15 carbons, which were assignable to two tertiary methyl groups [δH 1.27 (3H, s, H-14); δC 26.5 (C-14) and δH 1.57(3H, s, H-15); δC 22.1 (C-15), respectively], an exo methylene group [δH 6.21 (1H, d, J = 3.0 Hz, H-13b) and δH 5.49 (1H, d, J = 3.0 Hz, H-13a); δC 120.0], three acetal methine groups [δH 4.34 (1H, dd, J = 9.5, 11.5 Hz, H-6); δC 79.8 (C-6), δH 4.07 (1H, br s, H-3); δC 64.3 (C-3) and δH 3.70 (1H, br s, H-2); δC 64.6 (C-2), respectively], three oxygenated quaternary carbons δC 72.2 (C-10), 73.3 (C-1), and 83.3 (C-4), one carbonyl carbon δC 169.4 (C-12), two methine groups [δH 2.63 (1H, d, J = 11.5 Hz, H-5); δC 57.8 (C-5) and δH 3.45 (1H, m, H-7); δC 45.0 (C-7), respectively], two methylene groups [δH 1.84 (1H, m, H-9a), δH 2.05 (1H, m, H-9b); δC 35.0 (C-9) and δH 2.10 (1H, m, H-8a), δH 2.33 (1H, m, H-8b); δC 23.5 (C-8), respectively] and one quaternary carbon δC 139.3 (C-11). These observations suggested that compound 3 was a 1,2;3,4-diepoxyguaianolide sesquiterpene lactone with two tertiary methyls and one hydroxyl group. Furthermore, HMBC and NOESY spectral data were good agreement with the reported data (Li et al. 2010). Accordingly, compound 3 was determined as canin on the basis of the above evidences, together with a comparison with the literature (Li et al. 2010).

The known compounds 4–10 were also identified as eupatilin (4) (Li et al. 2010), quercetin-3-O-β-d-glucoside-7-O-α-l-rhamnoside (5) (Kim et al. 2013), isoquercitrin (6) (Duan et al. 2009), 1,3-di-O-caffeoylquinic acid (7) (An et al. 2008; Jiang et al. 2010; Lee et al. 2013), pinoresinol-4-O-β-d-glucoside (8) (Wang et al. 2012; Kim et al. 2005), scopolin (9) (Chung et al. 1999; Lee et al. 2005), and isofraxidin-7-O-β-d-glucopyranoside (10) (Heo et al. 2005; Hu et al. 2011), respectively, by comparing the NMR spectral data with those reported in the literature. All compounds have not been previously isolated from this plant.

IL-6 is a cytokine, originally identified as a T cell derived factor that regulates B-cell growth and differentiation (Hirano et al. 1986). Human IL-6 is an important component of the inflammatory cascade. Dysregulation of IL-6 production has been implicated in a variety of inflammatory/autoimmune disease states, including rheumatoid arthritis, cardiac myxoma, Castleman’s disease, and mesangial proliferative glomerulonephritis (Hirano et al. 1990). The proinflammatory cytokines IL-1 and TNF-α markedly stimulate the production IL-6 (Van Damme et al. 1987).

The inhibitory activity of the isolated compounds (1–10) against IL-6 production in TNF-α stimulated MG-63 cells was examined. None of these isolates exhibited cellular cytoxicity in MG 63 cells at the tested concentration (data not shown). Among these compounds, compounds 2, 3 and 7 showed potent inhibitory activity against IL-6 production in TNF-α stimulated MG-63 cells, while compounds 5, 6, and 9 showed moderate inhibitory activity (Fig. 3; Table 1).

Fig. 3
figure 3

Inhibitory effect of compounds 1–10 against IL-6 production in TNF-α stimulated MG-63cells. MG-63 cells (3 × 104) were incubated for 24 h. Cultures were incubated with or without compounds (100 μg/mL) for 30 min and then stimulated with TNF-α (10 ng/mL) for 24 h. IL-6 in the supernatant was measured by ELISA as described in “Materials and methods” section. Results are expressed as the mean ± S.E. from three different experiments. BAY 11-7085 was used as a positive control. *P < 0.05 or **P < 0.01 compared with TNF-α treated value

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Table 1 Inhibitory effect of compounds 1–10 against IL-6 production in TNF-α stimulated MG 63 cells
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In conclusion, this paper reports the isolation, characterization, and inhibitory activity of 10 isolates, including one new compound and nine known compounds, from the aerial parts of A. selengensis.